TAX (short for Taxi) - also known as PO12 - protocol droid was a basic humanoid-shaped droid design which was used in the production of various droid models - often for civilian use and seldom for military - by different droid manufacturers. Full production ID for this design was droid.protocol_droid.po12 (taxi). Like most humanoid-shaped models, it allowed to install wide array of internal weapons and protective shileds, besides the fact that it could use most blasters, rifles and melee weapons.
During and after the Cold War

The Cold War Event Cold War (3653BBY - 3642BBY)

this particular design was favored by taxi service companies across the galaxy. PO12s were also often used as personal assistants, administrators, and supervisors for other droids.